Defrosting frequency control method and device and variable frequency air source heat pump chiller heater

Abstract

This invention relates to the field of variable frequency air source heat pump chiller / hot water unit technology, specifically disclosing a method for controlling the defrosting frequency. The method includes: when the operating frequency of the chiller / hot water unit decreases to the minimum operating frequency for defrosting, controlling the chiller / hot water unit to enter the initial stage of defrosting operation, and monitoring the fin temperature of the finned heat exchanger in real time; when the fin temperature of the finned heat exchanger rises to a first preset temperature, controlling the chiller / hot water unit to enter the holding stage of defrosting operation; when the fin temperature of the finned heat exchanger rises to a second preset temperature, controlling the chiller / hot water unit to enter the final stage of defrosting operation; and when the fin temperature of the finned heat exchanger rises to a third preset temperature, controlling the chiller / hot water unit to exit the defrosting operation stage. This invention also discloses a defrosting frequency control device and a variable frequency air source heat pump chiller / hot water unit. This invention solves the problem of excessively long defrosting time and can effectively avoid high-pressure alarms and energy waste.

Description

Technical Field

[0001] This invention relates to the field of air source heat pump defrosting control technology, and in particular to a defrosting frequency control method, a defrosting frequency control device, and a variable frequency air source heat pump chiller / hot water unit including the defrosting frequency control device. Background Technology

[0002] Air source heat pumps, especially variable frequency air source heat pumps, have become widely used in northern China. They absorb heat energy from the outdoor air and transfer it indoors for heating. During winter operation, when the surface temperature of the outdoor heat exchanger is lower than the dew point temperature of the surrounding air and below 0°C, frost will form on the heat exchanger surface. Frost formation worsens the heat transfer efficiency of the heat exchanger and increases airflow resistance, reducing the heating capacity of the air source heat pump unit. In severe cases, the unit may even stop operating. To ensure normal operation and improve energy efficiency in winter, regular defrosting is necessary. Reverse cycle defrosting, also known as reversing defrosting, is a common defrosting method used in domestic household air conditioning systems. During defrosting, most defrosting control methods use a fixed compressor operating frequency, which can easily lead to the following problems: 1) The defrosting frequency is set too low, resulting in a longer defrosting time; 2) The defrosting frequency is set too high, easily leading to high-pressure protection and energy waste. In addition, some publicly available patents on defrosting logic control mention the use of defrosting frequency variation control, but the calculation model is relatively complex and difficult to implement in defrosting conditions where the monitoring parameters change rapidly, so it needs to be improved. Summary of the Invention

[0003] To address the deficiencies and shortcomings of existing technologies, this invention provides a defrosting frequency control method, a defrosting frequency control device, and a variable frequency air source heat pump chiller unit including the defrosting frequency control device. Based on the ambient temperature and outlet water temperature during defrosting, the optimal defrosting start frequency is determined, effectively solving the problem of excessively long defrosting times. Taking into account the rapid changes and delayed feedback of various unit parameters during the defrosting process, frequency control conditions are set for the intermediate defrosting process, effectively avoiding high-pressure alarms and energy waste.

[0004] As a first aspect of the present invention, a method for controlling the defrosting frequency is provided, wherein the defrosting frequency is controlled by a variable frequency air source heat pump chiller unit, the variable frequency air source heat pump chiller unit including a finned heat exchanger and a shell-and-tube heat exchanger, and the method for controlling the defrosting frequency includes:

[0005] When the variable frequency air source heat pump chiller is in heating mode, determine whether the operating frequency of the variable frequency air source heat pump chiller has dropped to the minimum operating frequency F required to start defrosting. min ;

[0006] When it is determined that the operating frequency of the variable frequency air source heat pump chiller unit has decreased to the minimum operating frequency F required to begin defrosting. min At that time, the variable frequency air source heat pump chiller unit is controlled to enter the initial stage of defrosting operation, and the fin temperature T of the finned heat exchanger is monitored in real time. def During the initial stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller unit gradually increases as the frequency rises slowly.

[0007] When the fin temperature T of the finned heat exchanger def When the temperature slowly rises to the first preset temperature, the variable frequency air source heat pump chiller unit is controlled to enter the defrosting operation holding phase; wherein, during the defrosting operation holding phase, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit remains constant despite the rapid increase in frequency.

[0008] When the fin temperature T of the finned heat exchanger def Rapidly rises to the second preset temperature T def降 At that time, the variable frequency air source heat pump chiller unit is controlled to enter the final stage of defrosting operation; wherein, in the final stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit gradually decreases as the frequency rises slowly.

[0009] When the fin temperature T of the finned heat exchanger def Slowly rise to the third preset temperature T def退 At that time, the variable frequency air source heat pump chiller unit is controlled to exit the defrosting operation stage.

[0010] Furthermore, the initial stage of defrosting operation also includes:

[0011] Real-time monitoring of the ambient temperature T of the finned heat exchanger a and the return water temperature T of the shell-and-tube heat exchanger in ;

[0012] At the initial stage of defrosting operation, based on the ambient temperature T of the finned heat exchanger... a and the return water temperature T of the shell-and-tube heat exchanger in The operating frequency F of the variable frequency air source heat pump chiller / hot water unit was determined. 除霜起始 .

[0013] Furthermore, at the initial stage of defrosting operation, based on the ambient temperature T of the finned heat exchanger... a and the return water temperature T of the shell-and-tube heat exchanger inThe operating frequency F of the variable frequency air source heat pump chiller / hot water unit was determined. 除霜起始 It also includes:

[0014] At the initial stage of defrosting operation, based on the ambient temperature T of the finned heat exchanger... a and the return water temperature T of the shell-and-tube heat exchanger in Consult the compressor operating frequency table during the initial stage to determine the operating frequency F of the variable frequency air source heat pump chiller unit. 除霜起始 .

[0015] Furthermore, in the final stage of defrosting operation, the operating frequency F of the variable frequency air source heat pump chiller / hot water unit... 除霜末期 The calculation formula is as follows:

[0016]

[0017] Among them, F 除霜起始 T is the operating frequency of the variable frequency air source heat pump chiller unit during the initial defrosting phase. def降 The second preset temperature, T def退 The third preset temperature, T def The real-time fin temperature of the finned heat exchanger.

[0018] Furthermore, the second preset temperature T def降 The second preset temperature T is the temperature setpoint for the defrosting and frequency reduction fins. def降 The temperature is 2℃.

[0019] Furthermore, the third preset temperature T def退 To de-frost and exit the fin temperature setpoint, the third preset temperature T def退 The temperature is 12℃.

[0020] As another aspect of the present invention, a defrosting frequency control device is provided, which controls the defrosting frequency through a variable frequency air source heat pump chiller unit, wherein the variable frequency air source heat pump chiller unit includes a finned heat exchanger and a shell-and-tube heat exchanger, and the defrosting frequency control device includes:

[0021] The judgment module is used to determine whether the operating frequency of the variable frequency air source heat pump chiller unit has decreased to the minimum operating frequency F required to start defrosting during heating operation. min ;

[0022] The first control module is used to determine when the operating frequency of the variable frequency air source heat pump chiller unit drops to the minimum operating frequency F required to start defrosting. min At that time, the variable frequency air source heat pump chiller unit is controlled to enter the initial stage of defrosting operation, and the fin temperature T of the finned heat exchanger is monitored in real time.def During the initial stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller unit gradually increases as the frequency rises slowly.

[0023] The second control module is used to control the fin temperature T of the finned heat exchanger. def When the temperature slowly rises to the first preset temperature, the variable frequency air source heat pump chiller unit is controlled to enter the defrosting operation holding phase; wherein, during the defrosting operation holding phase, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit remains constant despite the rapid increase in frequency.

[0024] The third control module is used to control the fin temperature T of the finned heat exchanger. def Rapidly rises to the second preset temperature T def降 At that time, the variable frequency air source heat pump chiller unit is controlled to enter the final stage of defrosting operation; wherein, in the final stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit gradually decreases as the frequency rises slowly.

[0025] The fourth control module is used to control the fin temperature T of the finned heat exchanger. def Slowly rise to the third preset temperature T def退 At that time, the variable frequency air source heat pump chiller unit is controlled to exit the defrosting operation stage.

[0026] In another aspect of the present invention, a variable frequency air source heat pump chiller / hot water unit is provided, comprising a compressor, a four-way reversing valve, a finned heat exchanger, a shell-and-tube heat exchanger, an electronic expansion valve, and a controller. The compressor is connected to the finned heat exchanger and the shell-and-tube heat exchanger respectively via the four-way reversing valve. The finned heat exchanger and the shell-and-tube heat exchanger are also connected via the electronic expansion valve. The finned heat exchanger is provided with a device for detecting the fin temperature T. def The controller includes the defrosting frequency control device described above;

[0027] When the controller determines that the compressor's operating frequency has dropped to the minimum operating frequency F required to begin defrosting... min When the variable frequency air source heat pump chiller unit enters the defrost operation phase, the four-way reversing valve switches to the defrost operation state. During the defrost operation phase, the high-temperature, high-pressure gaseous refrigerant discharged from the compressor enters the finned heat exchanger through the four-way reversing valve for defrosting. During the defrost operation phase, the fin temperature T of the finned heat exchanger... def The temperature continues to rise until the fin temperature T of the finned heat exchanger... defRise to the third preset temperature T def退 When the controller controls the variable frequency air source heat pump chiller unit to exit the defrosting operation stage, the four-way reversing valve switches to the heating operation state.

[0028] Furthermore, during the defrosting operation, the high-temperature, high-pressure gaseous refrigerant becomes a medium-temperature, high-pressure liquid refrigerant after passing through the finned heat exchanger. The medium-temperature, high-pressure liquid refrigerant then undergoes throttling and pressure reduction through the electronic expansion valve to form a low-temperature, low-pressure gas-liquid two-phase refrigerant. This low-temperature, low-pressure gas-liquid two-phase refrigerant then becomes a low-temperature, low-pressure gaseous refrigerant after passing through the shell-and-tube heat exchanger. Finally, the low-temperature, low-pressure gaseous refrigerant flows back into the compressor through the four-way reversing valve, thus completing one defrosting cycle.

[0029] The defrosting frequency control method provided by this invention has the following advantages: Based on the ambient temperature and return water temperature during defrosting, the optimal defrosting start frequency is determined. On the one hand, this avoids excessively long defrosting time due to a low defrosting frequency, which could cause the return water temperature to drop too quickly and affect the heating effect. On the other hand, it avoids high-pressure alarms caused by a high defrosting frequency. After the frost layer on the finned heat exchanger has basically melted, the fin temperature rises rapidly, and the fin temperature detection has a lag characteristic. By setting frequency control conditions for the intermediate defrosting process and using frequency reduction correction, the rate of fin temperature rise can be effectively suppressed, effectively avoiding excessive dry steaming of the heat exchanger caused by excessive heat supply, thus avoiding the risk of high-pressure alarms and energy waste. Attached Figure Description

[0030] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0031] Figure 1 A flowchart of the defrosting frequency control method provided by the present invention.

[0032] Figure 2 A flowchart illustrating a specific implementation method for the defrosting frequency control method provided by the present invention.

[0033] Figure 3 This is a schematic diagram of the operation of the variable frequency air source heat pump chiller / hot water unit during a defrosting cycle, as provided by the present invention.

[0034] Figure 4 This is a schematic diagram of the structure of the variable frequency air source heat pump chiller / hot water unit provided by the present invention.

[0035] In the diagram: 1-Compressor; 2-Four-way reversing valve; 3-Finned heat exchanger; 4-Built-and-shell heat exchanger; 5-Electronic expansion valve; 6-Finned temperature sensor. Detailed Implementation

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0038] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0039] This embodiment provides a method for controlling the defrosting frequency, which is achieved through a variable frequency air source heat pump chiller unit. The variable frequency air source heat pump chiller unit includes a finned heat exchanger and a shell-and-tube heat exchanger. Figure 1 A flowchart of the defrosting frequency control method provided by the present invention is shown below. Figure 1 As shown, the method for controlling the defrosting frequency includes:

[0040] Step S1: When the variable frequency air source heat pump chiller is in heating mode, determine whether the operating frequency of the variable frequency air source heat pump chiller has decreased to the minimum operating frequency F required to start defrosting. min ;

[0041] Step S2: When it is determined that the operating frequency of the variable frequency air source heat pump chiller unit has dropped to the minimum operating frequency F required to start defrosting. min At that time, the variable frequency air source heat pump chiller unit is controlled to enter the initial stage of defrosting operation, and the fin temperature T of the finned heat exchanger is monitored in real time. def During the initial stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller unit gradually increases as the frequency rises slowly.

[0042] Preferably, at the initial stage of defrosting operation, the method further includes:

[0043] Real-time monitoring of the ambient temperature T of the finned heat exchanger a and the return water temperature T of the shell-and-tube heat exchanger in ;

[0044] At the initial stage of defrosting operation, based on the ambient temperature T of the finned heat exchanger... a and the return water temperature T of the shell-and-tube heat exchanger in The operating frequency F of the variable frequency air source heat pump chiller / hot water unit was determined. 除霜起始 .

[0045] Specifically, at the initial stage of defrosting operation, based on the ambient temperature T of the finned heat exchanger... a and the return water temperature T of the shell-and-tube heat exchanger in The operating frequency F of the variable frequency air source heat pump chiller / hot water unit was determined. 除霜起始 It also includes:

[0046] At the initial stage of defrosting operation, based on the ambient temperature T of the finned heat exchanger... a and the return water temperature T of the shell-and-tube heat exchanger in Consult the compressor operating frequency table during the initial stage to determine the operating frequency F of the variable frequency air source heat pump chiller unit. 除霜起始 .

[0047] The compressor operating frequency during the initial stage is shown in Table 1-2.

[0048] Table 1

[0049] <![CDATA[T a ≥7]]> <![CDATA[F 起始00 ]]> <![CDATA[F 起始01 ]]> <![CDATA[F 起始02 ]]> <![CDATA[F 起始03 ]]> <![CDATA[2℃<T a ≤7℃]]> <![CDATA[F 起始10 ]]> <![CDATA[F 起始11 ]]> <![CDATA[F 起始12 ]]> <![CDATA[F 起始13 ]]> <![CDATA[-7℃<T a ≤2℃]]> <![CDATA[F 起始20 ]]> <![CDATA[F 起始21 ]]> <![CDATA[F 起始22 ]]> <![CDATA[F 起始23 <!-- 4 -->]]> <![CDATA[T a <-7℃]]> <![CDATA[F 起始30 ]]> <![CDATA[F 起始31 ]]> <![CDATA[F 起始32 ]]> <![CDATA[F 起始33 ]]>

[0050] Table 2

[0051] <![CDATA[T a ≥7]]> 65 65 60 60 <![CDATA[2℃<T a ≤7℃]]> 70 65 65 60 <![CDATA[-7℃<T a ≤2℃]]> 75 70 65 60 <![CDATA[T a <-7℃]]> 80 75 70 65

[0052] As shown in Table 1-2 above, with the outdoor ambient temperature T a Reduce the initial defrosting frequency F of the unit. 除霜起始 The trend of increasing frequency is because the lower the ambient temperature, the more heat is required for defrosting, and increasing the initial defrosting frequency can shorten the initial defrosting operation time; with the return water temperature T... in Increase, initial defrosting frequency F of the unit 除霜起始 The trend of decreasing temperature is because the higher the return water temperature, the more heat is absorbed from the shell-and-tube heat exchanger during defrosting, which in turn increases the amount of heat discharged to the finned heat exchanger 3. If the defrosting frequency is not reduced, it will lead to an alarm for excessively high exhaust pressure.

[0053] Step S3: When the fin temperature T of the finned heat exchanger def When the temperature slowly rises to the first preset temperature, the variable frequency air source heat pump chiller unit is controlled to enter the defrosting operation holding phase; wherein, during the defrosting operation holding phase, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit remains constant despite the rapid increase in frequency.

[0054] Step S4: When the fin temperature T of the finned heat exchanger def Rapidly rises to the second preset temperature T def降 At that time, the variable frequency air source heat pump chiller unit is controlled to enter the final stage of defrosting operation; wherein, in the final stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit gradually decreases as the frequency rises slowly.

[0055] Specifically, during the final stage of defrosting operation, the operating frequency F of the variable frequency air source heat pump chiller / hot water unit... 除霜末期 The calculation formula is as follows:

[0056]

[0057] Among them, F 除霜起始 T is the operating frequency of the variable frequency air source heat pump chiller unit during the initial defrosting phase. def降 The second preset temperature, T def退 The third preset temperature, T def The real-time fin temperature of the finned heat exchanger.

[0058] Specifically, the second preset temperature T def降 The second preset temperature T is the temperature setpoint for the defrosting and frequency reduction fins. def降 The temperature is 2℃.

[0059] Step S5: When the fin temperature T of the finned heat exchanger def Slowly rise to the third preset temperature T def退 At that time, the variable frequency air source heat pump chiller unit is controlled to exit the defrosting operation stage.

[0060] Specifically, the third preset temperature T def退 To de-frost and exit the fin temperature setpoint, the third preset temperature T def退 The temperature is 12℃.

[0061] In this embodiment of the invention, the final stage of the defrosting operation lasts for 10 seconds.

[0062] In this embodiment of the invention, during the final stage of defrosting operation, the operating frequency F of the variable frequency air source heat pump chiller / hot water unit is...除霜末期 ≥30Hz.

[0063] In embodiments of the present invention, such as Figure 3 As shown, a defrosting cycle of a variable frequency air source heat pump chiller unit in winter can be divided into five stages: pre-defrosting heating, defrosting preparation, defrosting operation, heating preparation, and post-defrosting heating. The defrosting operation stage is further divided into three processes: defrosting start, defrosting maintenance, and defrosting end.

[0064] (1) During the defrosting preparation stage, the operating frequency of the variable frequency air source heat pump chiller unit is reduced from point A to the minimum operating frequency B at the start of defrosting, and the defrosting conditions are met. The four-way reversing valve 2 is switched to the refrigeration operation state.

[0065] (2) During the defrosting process when the operating frequency of the variable frequency air source heat pump chiller unit increases from point B to point C, high-temperature and high-pressure gaseous refrigerant enters the finned heat exchanger 3 for defrosting. The frost layer on the finned heat exchanger 3 gradually melts into ice water. At this time, the fin temperature T of the finned heat exchanger 3 is... def It is a slow ascent process;

[0066] (3) The process from point C to point D is the defrosting and maintenance process. During this process, the unit frequency remains constant, and the ice water on the finned heat exchanger 3 gradually flows out completely, and the fin temperature T def The temperature rises rapidly;

[0067] (4) When the defrosting process reaches point D, the fin temperature reaches the second preset temperature T. def降 Unit frequency F 除霜末期 Start based on fin temperature T def It changes as it changes, until it is reduced to the minimum operating frequency E point at the end of defrosting;

[0068] (5) When the defrosting exit condition is met, the four-way reversing valve 2 switches back to the heating operation state, and the unit frequency starts from point E to the heating frequency F after defrosting.

[0069] Preferably, such as Figure 2 As shown, the present invention provides a method for controlling the defrosting frequency, specifically including the following steps:

[0070] Step 201: Unit heating operation;

[0071] Step 202: Determine whether the defrosting conditions are met, that is, determine whether the operating frequency of the variable frequency air source heat pump chiller unit has decreased to the minimum operating frequency F required to start defrosting. min If the defrosting conditions are met, proceed to step 203; otherwise, return to step 202.

[0072] Step 203, detect the ambient temperature T a and return water temperature T inDetermine the defrosting start frequency F 除霜起始 ;

[0073] Step 204: Perform the defrosting procedure;

[0074] Step 205, detect the fin temperature T def Whether the defrosting frequency reduction condition has been met, i.e., the fin temperature T is measured. def Has the second preset temperature T been reached? def降 If the defrosting frequency reduction condition is met, proceed to step 206; otherwise, return to step 205.

[0075] Step 206: Calculate the defrosting frequency F of the variable frequency air source heat pump chiller unit. 除霜末期 ;

[0076] Step 207, detect the fin temperature T def Whether the defrosting exit condition has been met, i.e., the fin temperature T is measured. def Has the third preset temperature T been reached? def退 If the defrosting exit conditions are met, proceed to step 208; otherwise, return to step 207.

[0077] Step 208: Exit the defrost process.

[0078] In this embodiment of the invention, based on the ambient temperature T a Return water temperature T in and the fin temperature T at the end of defrosting def Changes are made by controlling the unit's operating frequency during the defrosting process and suppressing the fin temperature T at the end of defrosting. def The temperature rises too quickly to achieve the best defrosting effect.

[0079] As another embodiment of the present invention, a defrosting frequency control device is provided, which controls the defrosting frequency through a variable frequency air source heat pump chiller unit, wherein the variable frequency air source heat pump chiller unit includes a finned heat exchanger and a shell-and-tube heat exchanger, and the defrosting frequency control device includes:

[0080] The judgment module is used to determine whether the operating frequency of the variable frequency air source heat pump chiller unit has decreased to the minimum operating frequency F required to start defrosting during heating operation. min ;

[0081] The first control module is used to determine when the operating frequency of the variable frequency air source heat pump chiller unit drops to the minimum operating frequency F required to start defrosting. min At that time, the variable frequency air source heat pump chiller unit is controlled to enter the initial stage of defrosting operation, and the fin temperature T of the finned heat exchanger is monitored in real time. defDuring the initial stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller unit gradually increases as the frequency rises slowly.

[0082] The second control module is used to control the fin temperature T of the finned heat exchanger. def When the temperature slowly rises to the first preset temperature, the variable frequency air source heat pump chiller unit is controlled to enter the defrosting operation holding phase; wherein, during the defrosting operation holding phase, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit remains constant despite the rapid increase in frequency.

[0083] The third control module is used to control the fin temperature T of the finned heat exchanger. def Rapidly rises to the second preset temperature T def降 At that time, the variable frequency air source heat pump chiller unit is controlled to enter the final stage of defrosting operation; wherein, in the final stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit gradually decreases as the frequency rises slowly.

[0084] The fourth control module is used to control the fin temperature T of the finned heat exchanger. def Slowly rise to the third preset temperature T def退 At that time, the variable frequency air source heat pump chiller unit is controlled to exit the defrosting operation stage.

[0085] As another embodiment of the present invention, a variable frequency air source heat pump chiller / hot water unit is provided, such as... Figure 4 As shown, the system includes a compressor 1, a four-way reversing valve 2, a finned heat exchanger 3, a shell-and-tube heat exchanger 4, an electronic expansion valve 5, and a controller. The compressor 1 is connected to the finned heat exchanger 3 and the shell-and-tube heat exchanger 4 via the four-way reversing valve 2. The finned heat exchanger 3 and the shell-and-tube heat exchanger 4 are also connected via the electronic expansion valve 5. The finned heat exchanger 3 is equipped with a device for detecting the fin temperature T. def The fin temperature sensor 6, and the controller includes the defrosting frequency control device described above;

[0086] When the controller determines that the operating frequency of compressor 1 has dropped to the minimum operating frequency F required to start defrosting min When the variable frequency air source heat pump chiller unit enters the defrost operation phase, the four-way reversing valve 2 switches to the defrost operation state. During the defrost operation phase, the high-temperature and high-pressure gaseous refrigerant discharged by the compressor 1 enters the finned heat exchanger 3 through the four-way reversing valve 2 for defrosting. During the defrost operation phase, the fin temperature T of the finned heat exchanger 3 is... defThe temperature continues to rise until the fin temperature T of the finned heat exchanger... def Rise to the third preset temperature T def退 When the controller controls the variable frequency air source heat pump chiller unit to exit the defrosting operation stage, the four-way reversing valve 2 switches to the heating operation state.

[0087] Specifically, during the defrosting operation, the high-temperature and high-pressure gaseous refrigerant becomes a medium-temperature and high-pressure liquid refrigerant after passing through the finned heat exchanger 3. The medium-temperature and high-pressure liquid refrigerant is then throttled and depressurized by the electronic expansion valve 5 to form a low-temperature and low-pressure gas-liquid two-phase refrigerant. The low-temperature and low-pressure gas-liquid two-phase refrigerant becomes a low-temperature and low-pressure gaseous refrigerant after passing through the shell-and-tube heat exchanger 4. The low-temperature and low-pressure gaseous refrigerant then flows back to the compressor 1 through the four-way reversing valve 2, thus completing one defrosting cycle.

[0088] This invention provides a method for controlling the defrosting frequency. Based on the ambient temperature and return water temperature during defrosting, the optimal defrosting start frequency is determined. On the one hand, this avoids excessively long defrosting times due to a low defrosting frequency, which could cause a rapid drop in return water temperature and affect heating performance. On the other hand, it avoids high-pressure alarms caused by a high defrosting frequency. After the frost layer on the finned heat exchanger has basically melted, the fin temperature rises rapidly, and fin temperature detection has a lag characteristic. By setting frequency control conditions during the defrosting process and using frequency reduction correction, the rate of fin temperature rise can be effectively suppressed. This effectively avoids excessive heat supply to the heat exchanger, preventing excessive dry steaming and avoiding the risk of high-pressure alarms and energy waste.

[0089] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for controlling defrosting frequency, characterized in that, The defrosting frequency is controlled by a variable frequency air source heat pump chiller unit, which includes a finned heat exchanger and a shell-and-tube heat exchanger. The method for controlling the defrosting frequency includes: When the variable frequency air source heat pump chiller is in heating mode, determine whether the operating frequency of the variable frequency air source heat pump chiller has dropped to the minimum operating frequency F required to start defrosting. min ; When it is determined that the operating frequency of the variable frequency air source heat pump chiller unit has decreased to the minimum operating frequency F required to begin defrosting. min At that time, the variable frequency air source heat pump chiller unit is controlled to enter the initial stage of defrosting operation, and the fin temperature T of the finned heat exchanger is monitored in real time. def During the initial stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller unit gradually increases as the frequency rises slowly. When the fin temperature T of the finned heat exchanger def When the temperature slowly rises to the first preset temperature, the variable frequency air source heat pump chiller unit is controlled to enter the defrosting operation holding phase; wherein, during the defrosting operation holding phase, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit remains constant despite the rapid increase in frequency. When the fin temperature T of the finned heat exchanger def Rapidly rises to the second preset temperature T def降 At that time, the variable frequency air source heat pump chiller unit is controlled to enter the final stage of defrosting operation; wherein, in the final stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit gradually decreases as the frequency rises slowly. When the fin temperature T of the finned heat exchanger def Slowly rise to the third preset temperature T def退 At that time, the variable frequency air source heat pump chiller unit is controlled to exit the defrosting operation stage.

2. The method for controlling defrosting frequency according to claim 1, characterized in that, The initial stage of defrosting operation also includes: Real-time monitoring of the ambient temperature T of the finned heat exchanger a and the return water temperature T of the shell-and-tube heat exchanger in ; At the initial stage of defrosting operation, based on the ambient temperature T of the finned heat exchanger... a and the return water temperature T of the shell-and-tube heat exchanger in The operating frequency F of the variable frequency air source heat pump chiller / hot water unit was determined. 除霜起始 .

3. The method for controlling the defrosting frequency according to claim 2, characterized in that, During the initial stage of defrosting operation, the ambient temperature T of the finned heat exchanger is determined. a and the return water temperature T of the shell-and-tube heat exchanger in The operating frequency F of the variable frequency air source heat pump chiller / hot water unit was determined. 除霜起始 It also includes: At the initial stage of defrosting operation, based on the ambient temperature T of the finned heat exchanger... a and the return water temperature T of the shell-and-tube heat exchanger in Consult the compressor operating frequency table during the initial stage to determine the operating frequency F of the variable frequency air source heat pump chiller unit. 除霜起始 .

4. The method for controlling the defrosting frequency according to claim 2, characterized in that, During the final stage of defrosting operation, the operating frequency F of the variable frequency air source heat pump chiller unit... 除霜末期 The calculation formula is as follows: Among them, F 除霜起始 T is the operating frequency of the variable frequency air source heat pump chiller unit during the initial defrosting phase. def降 The second preset temperature, T def退 The third preset temperature, T def The real-time fin temperature of the finned heat exchanger.

5. The method for controlling defrosting frequency according to claim 1, characterized in that, The second preset temperature T def降 The second preset temperature T is the temperature setpoint for the defrosting and frequency reduction fins. def降 The temperature is 2℃.

6. The method for controlling defrosting frequency according to claim 1, characterized in that, The third preset temperature T def退 To de-frost the fin temperature setpoint, the third preset temperature T def退 The temperature is 12℃.

7. A defrosting frequency control device, characterized in that, The defrosting frequency is controlled by a variable frequency air source heat pump chiller unit, which includes a finned heat exchanger and a shell-and-tube heat exchanger. The defrosting frequency control device includes: The judgment module is used to determine whether the operating frequency of the variable frequency air source heat pump chiller unit has decreased to the minimum operating frequency F required to start defrosting during heating operation. min ; The first control module is used to determine when the operating frequency of the variable frequency air source heat pump chiller unit drops to the minimum operating frequency F required to start defrosting. min At that time, the variable frequency air source heat pump chiller unit is controlled to enter the initial stage of defrosting operation, and the fin temperature T of the finned heat exchanger is monitored in real time. def During the initial stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller unit gradually increases as the frequency rises slowly. The second control module is used to control the fin temperature T of the finned heat exchanger. def When the temperature slowly rises to the first preset temperature, the variable frequency air source heat pump chiller unit is controlled to enter the defrosting operation holding phase; wherein, during the defrosting operation holding phase, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit remains constant despite the rapid increase in frequency. The third control module is used to control the fin temperature T of the finned heat exchanger. def Rapidly rises to the second preset temperature T def降 At that time, the variable frequency air source heat pump chiller unit is controlled to enter the final stage of defrosting operation; wherein, in the final stage of defrosting operation, the fin temperature T of the finned heat exchanger is... def The frequency of the variable frequency air source heat pump chiller / hot water unit gradually decreases as the frequency rises slowly. The fourth control module is used to control the fin temperature T of the finned heat exchanger. def Slowly rise to the third preset temperature T def退 At that time, the variable frequency air source heat pump chiller unit is controlled to exit the defrosting operation stage.

8. A variable frequency air source heat pump chiller / hot water unit, characterized in that, The system includes a compressor (1), a four-way reversing valve (2), a finned heat exchanger (3), a shell-and-tube heat exchanger (4), an electronic expansion valve (5), and a controller. The compressor (1) is connected to the finned heat exchanger (3) and the shell-and-tube heat exchanger (4) respectively through the four-way reversing valve (2). The finned heat exchanger (3) and the shell-and-tube heat exchanger (4) are also connected through the electronic expansion valve (5). The finned heat exchanger (3) is equipped with a device for detecting the fin temperature T. def The fin temperature sensor (6), the controller includes the defrosting frequency control device as described in claim 7; When the controller determines that the operating frequency of the compressor (1) has dropped to the minimum operating frequency F required to start defrosting min When the variable frequency air source heat pump chiller unit enters the defrosting operation stage, the four-way reversing valve (2) switches to the defrosting operation state. During the defrosting operation, the high-temperature and high-pressure gaseous refrigerant discharged by the compressor (1) enters the finned heat exchanger (3) through the four-way reversing valve (2) for defrosting. During the defrosting operation, the fin temperature T of the finned heat exchanger (3) is... def The temperature continues to rise until the fin temperature T of the finned heat exchanger... def Rise to the third preset temperature T def退 When the controller controls the variable frequency air source heat pump chiller unit to exit the defrost operation stage, the four-way reversing valve (2) switches to the heating operation state.

9. The variable frequency air source heat pump chiller / hot water unit according to claim 8, characterized in that, During the defrosting operation, the high-temperature and high-pressure gaseous refrigerant becomes a medium-temperature and high-pressure liquid refrigerant after passing through the finned heat exchanger (3). The medium-temperature and high-pressure liquid refrigerant is throttled and depressurized by the electronic expansion valve (5) to form a low-temperature and low-pressure gas-liquid two-phase refrigerant. The low-temperature and low-pressure gas-liquid two-phase refrigerant becomes a low-temperature and low-pressure gaseous refrigerant after passing through the shell-and-tube heat exchanger (4). The low-temperature and low-pressure gaseous refrigerant flows back to the compressor (1) after passing through the four-way reversing valve (2), thus completing one defrosting cycle.

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